1. Field of the Invention
The present invention concerns external techniques to warm the human body for comfort, therapy, surgery, or other treatment. More particularly, the invention concerns a warm air blower that is mounted to the foot of a bed and utilized to direct warm air to the lower extremities of a supine person.
2. Description of the Related Art
Many people complain of having “cold feet” while laying in bed. For some people, they simply feel colder at any given temperature than other people. For others, the problem is more serious because they suffer from inadequate circulation to the legs and feet, resulting in abnormally cold feet and legs. In either case, the perception of cold feet can cause significant discomfort, especially while trying to sleep.
Normal body core temperature (“normothermia”) occurs at about 37° Celsius. Body temperatures below this are considered “hypothermic,” and have many negative physiological effects beyond mere discomfort. Temperature excursions of a mere 1–2° Celsius below normal can profoundly affect many cellular and physiological functions in areas such as the immune system, coagulation system, cardiovascular system, and death rates during surgery. According to one published study, surgical patients with a core temperature of 34–35° Celsius experienced three times more wound infections than persons maintained at 36° Celsius.
Historically, the definition of “normothermia” has been limited to the core thermal compartment of the body. The peripheral thermal compartment, including the legs and other extremities, is designed to act as buffer or insulator between the core and the environment. Therefore, the peripheral compartment is expected to be hypothermic under many circumstances. This is one example of an “evolutionary tradeoff.” Namely, in order to maintain their core temperatures within a narrow range, warm blooded animals readily sacrifice warmness of the extremities.
This natural tendency toward peripheral hypothermia is exacerbated by vascular disease, which further reduces blood flow to the extremities. In fact, the combination of sacrificial hypothermia of the extremities and peripheral vascular disease can result in especially profound hypothermia of the legs. Persons with vascular insufficiency of the legs generally have colder legs, sometimes even approaching room temperature. These same persons are also prone to chronic non-healing skin wounds on their legs. These wounds may originate for various reasons, such as diabetes causing small vessel disease, external pressure causing local vascular occlusion, venous disease, and circulatory insufficiency reducing the blood flow and changing the hydrostatic gradients.
Whether peripheral hypothermia results from vascular disease, sacrificial hypothermia, or both, this condition inhibits important cellular functions of leg tissue. These cellular functions are not any different, or less important, than functions of cells in core vital organs. For example, a circulating immune cell does not know if it is fighting an infection in the heart or lungs, or the big toe. However, the extremities are more often hypothermic than the core vital organs, and therefore suffer more frequently from hypothermia-induced limitations.
Hypothermia in the lower extremities, then, is especially prevalent due to sacrificial hypothermia, peripheral vascular disease, or a combination of both. Peripheral hypothermia causes pain and possible interference with cellular functions of leg tissues.